Deserialization of Untrusted Data in Microsoft SharePoint Server - CVE-2026-85900
Published: October 14, 2026
Vulnerability identifier: #VU155223
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-85900
CWE-ID: CWE-502
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to execute arbitrary code.
The vulnerability exists due to deserialization of untrusted data in Microsoft Office SharePoint when processing untrusted serialized data. A remote user can supply untrusted serialized data over the network to execute arbitrary code.
Exploitation requires at least Site Member permissions. The Preview Pane is not an attack vector.
Affected software
Microsoft SharePoint Server
How to mitigate CVE-2026-85900
Install security update from vendor's website.
Microsoft SharePoint Server - update to 16.0.20326.20190